Encrypted Disc Images the best protection?

Posted:
in Mac Software edited January 2014
Okay, so I am organizing all of the files on my computer, and thought that I would place all of my work encrypted inside of an encrypted disk image. That way, if my computer were ever compromised, my data would be safe. When I plan on working, I will just enter the password and mount it.



I have a few questions though. I am just a little bit unsure about how safe this would be--safe for my data. How likely is it that an image containing many, many files would become corrupt, becoming an encrypted, mixed-up mess, making me lose all of my data? Does having more data in an encrypted disk image increase any risk of such corruption?



Also, wouldn't this make it easier and more secure for my data once in its backed-up location? I could just back up the disk image onto an external hard drive periodically. This would make me have to manage less files to backup if I went the manual backup route (i am still running Tiger), and my encrypted disk image would require the same password to unlock it on the external hard drive, keeping it just as secure.



It all seems like a good idea to me, but I thought I would run it by you folks in case there are things I have not considered.



Some downsides that I can see to this is that a disc image that is 3 GB's in size would require the entire thing being backed up, even if I made subtle changes to the contents therein.



Anything else I should think about or consider? What other downsides are there to this method? Does anyone really do this with so much data? (I would be doing this with my pro audio projects and stuff related).



Thanks for letting me bounce this off of you guys!

Comments

  • Reply 1 of 10
    MarvinMarvin Posts: 14,195moderator
    Quote:
    Originally Posted by AppleComputer View Post


    OHow likely is it that an image containing many, many files would become corrupt, becoming an encrypted, mixed-up mess, making me lose all of my data? Does having more data in an encrypted disk image increase any risk of such corruption?



    Having a bigger image means that it increases the likelihood that corrupted sectors on your hard drive will affect the image. It's a pretty unlikely occurrence though. Keeping a backup or two is safe and if you keep them under 4.2GB, you can backup to DVD - you can use DVDRW if you do it periodically, just use two discs so you don't erase your backup while you write the new one.



    Quote:
    Originally Posted by AppleComputer View Post


    Also, wouldn't this make it easier and more secure for my data once in its backed-up location? I could just back up the disk image onto an external hard drive periodically.



    Yes, it's pretty easy and fast to backup.



    Quote:
    Originally Posted by AppleComputer View Post


    Some downsides that I can see to this is that a disc image that is 3 GB's in size would require the entire thing being backed up, even if I made subtle changes to the contents therein.



    One thing you can do is mount both images and then use clone software to copy the changes from one to the other. 3GB takes under 5 minutes to copy over though so it's less hassle doing a full copy.



    Quote:
    Originally Posted by AppleComputer View Post


    Anything else I should think about or consider? What other downsides are there to this method? Does anyone really do this with so much data? (I would be doing this with my pro audio projects and stuff related).



    Don't use sparse images. They corrupt more easily than fixed size images. Besides that, there aren't really any downsides except that you do waste drive space when you don't fill up the image. It would be nice if Apple offered filesystem level folder encryption and it encrypted files individually.
  • Reply 2 of 10
    As Marvin says!



    However, do not rely on DVDs for long term storage! Burned DVDs – as opposed to pressed DVDs – start degrading by osmosis from day One! Which means that they won't be readable anymore after somewhere between 5 and 10 years!



    So DVDs are not suitable for long term storage. Only for medium term storage (up to, say, 3 years).



    And if you want to minimise the risk of discovering that a backup DVD was corrupted: make two identical copies.
  • Reply 3 of 10
    You seem to have a pretty good handle on what you're getting into ... all your own statements were accurate.



    I'll just give you my experience... I've been using File Vault (nothing more than putting your entire home folder in an encrypted image that automatically mounts at login.) on my PBook for a couple years... backing it up once a month or so to an external HDD (pretty much the same plan you have)...

    I have NEVER had a problem with image corruption. The process works flawlessly for me.
  • Reply 4 of 10
    frank777frank777 Posts: 5,770member
    Yeah, I've been wondering about activating FileVault. It should be usable by now.



    How does it work with Time Machine? Are you backing up open files or encrypted files?
  • Reply 5 of 10
    Thank you everyone for all of your responses! I am feeling pretty confident about locking most of my stuff up now!



    On the FileVault topic, I have a friend who had Filevault go bad, essentially locking herself out of her own computer files. She went to see an Apple Genius, who was able to undo the damage, and than recommended that she not use Filevault.



    Does that go along with the notion that Filevault is/was a little iffy? Is it infact more sound now?





    Thanks, again!
  • Reply 6 of 10
    Quote:
    Originally Posted by AppleComputer View Post


    Does that go along with the notion that Filevault is/was a little iffy? Is it infact more sound now?





    Thanks, again!





    Don't know... all I can say is I've used it for 2+ years without a hiccup.
  • Reply 7 of 10
    MarvinMarvin Posts: 14,195moderator
    Quote:
    Originally Posted by AppleComputer View Post


    On the FileVault topic, I have a friend who had Filevault go bad, essentially locking herself out of her own computer files. She went to see an Apple Genius, who was able to undo the damage, and than recommended that she not use Filevault.



    The problem with FileVault is that it has a sparse image mounted all the time you are using your machine. If you have to force reboot, it doesn't unmount properly and can become corrupt. The very small amount of times you have to force reboot in OS X means you aren't likely to come across the problem but if it happens, it's not a good feeling knowing that your data is gone so quickly.



    I did a test a couple of years back with fixed size images and sparse images and with the sparse image mounted, I did a power down. It took about 5 or 6 reboots but it corrupted the image so it couldn't be mounted. Tried it on another sparse image and it did the same thing. When I ran the fixed images through the same tests, they didn't get corrupted. It may just have been coincidence but I don't trust sparse images. There are a number of people who have noted similar issues:



    http://discussions.apple.com/thread....readID=1488529

    http://toxicsoftware.com/filevault_corruption/

    http://www.tidbits.com/[email protected]@.3c7c4c7a/21



    "But this is an easy (if likely) scenario. So I tried something more

    complex. I created a 100 MB sparse image and saved a text file to it,

    as above. I then started a 90 MB file copy to the image. Before the

    copy could complete, I restarted my Mac.



    After the reboot, the image fails to mount, claiming "no mountable

    filesystems." Corruption at last!"



    It could be to do with the way it writes the image. Fixed images have already allocated the file space so if a partial file goes into the image, it shouldn't matter. A sparse image hasn't allocated the space so if you interrupt a transfer while it is modifying the disk image file size itself, that's possibly what is corrupting it.



    There are a number of other things I don't like about it such as having difficulties doing backups - your home folder has a lot of things you generally don't need encrypted like app preferences and caches. Plus, it being unlocked at startup just seems to go against the whole point of encryption. If you have auto-login, there's little point to using encryption because if your machine fails and you have to send it for repair or it's stolen, someone booting your drive has access to your files.



    Then you can have issues if you try to make another account or change your passwords/usernames. Not to mention that you will be using too much space. Sparse images still have a fixed size and say you have your itunes library in your home folder, all your music goes into it. If you move the music out, it doesn't free up that space unless you manually do an image cleanup process, which takes ages and doesn't always work.



    I would always strongly recommend manually controlled fixed size encrypted disk images over FileVault. They aren't ideal for every situation such as encrypting massive amounts of data that changes daily but in those cases there are drive-level encryption solutions. For smaller work files like photos and audio, they are fine.
  • Reply 8 of 10
    sequitursequitur Posts: 1,901member
    I have tried using TrueCrypt to encrypt a 30GB file to an external HDD. No joy.

    It takes about 3 hours for TrueCrypt to set up a 30GB "container". Then, it took 2 1/2 hours to transfer the file into the container.



    When I got an error message every 30 seconds that I was running out of space on that HDD (I'll call BU 1) although it still had 1/2 GB of space left on it, I erased that "container" and put one on a larger partition. Of course, it took almost an hour to erase the first container and the 3 hour and 2 1/2 hour process to save the file - encrypted.



    Everything went smoothly until I tried adding a 1GB file on BU 1 outside the "container". That caused the 30GB container to disappear into thin air - pouf - without taking the time that the first container took to delete.



    Figuring I screwed up by adding that smaller file, I went through the process again.

    This time, I put the smaller file in first and then built the container. Eureka, it worked. Then, leaving the encrypted file open, I attempted to back up the file incrementally. Pouf - the container again disappeared into thin air instantaneously.



    You would think I'd learned my lesson by now and scrap TrueCrypt. But, noooo, I had a tiger (excuse the expression - I use Tiger OS) by the tail, I went through the process again. Fortunately, the process was running in the background, and it wasn't interfering with my regular usage.



    Again, I tried backing the file up incrementally using CCC. IT WORKED. I was almost purring that I finally got TrueCrypt to do what I wanted.



    Then, I committed THE fatal error. I restarted my computer after a security update.

    Can you spell 'POUF'. Yes, not only did the encrypted "container" disappear into thin air, but everything in the TrueCrypt dialog box and menus turned 'gray' and nothing worked after that.



    You're thinking, "This guy is a bear for punishment, and he'll try it again." Noooo. TrueCrypt, you can take your encryptor and shove it up your "container."



    Thanks for listening, guys. I had to get this off my chest.



    Edit: BTW, while TrueCrypt WAS working, the encryption was very good. It just couldn't be trusted to remain working.
  • Reply 9 of 10
    Okay, thanks a lot Marvin. I will only use Read/Write encrypted images.



    Marvin, what you are saying is, that if I have my encrypted images mounted (which I plan on being the case pretty much all of the time--I hardly ever restart my computer, I just put it to sleep), and it crashes or I am forced to do a hard restart (which I have to say, is more often that I would expect from my Mac--though Apple very recently replaced my processors, as one went bad, so maybe it was a slow death that caused more and more frequent crashes until they completely died), that there is a darn good chance that the read/write encrypted image will become corrupted? [sorry for the run-on sentence. There is a concise question in there somewhere].



    Or, are you saying that there is only really a chance of corruption if I am actively making transfers/changes to the mounted image at the time of a crash?



    This is the kind of stuff I am most curious/concerned about. I pretty much plan on always having these encrypted images mounted. Also, did I mention that I plan on having the encrypted images on my secondary, internal hard drive? Does that make any kind of difference--mounting images ONTO the desktop FROM a secondary hard drive, and always accessing the data that way?



    Also, as I mentioned earlier, I am still using Tiger on a PPC. Will my Disk Utility-encrypted images make the transfer seamlessly when I make the jump to a new Mac down the line? From PPC to Intel, etc?



    The likely hood my my computer being stolen from my home, or my unencrypted backups falling into the wrong hands, is not great. Would I be at more of a data-loss risk with my proposed storage/encryption method of mostly always having these images mounted?



    Thank you Marvin, and the rest of you guys! You truly are a wellspring of experience and information!
  • Reply 10 of 10
    MarvinMarvin Posts: 14,195moderator
    Quote:
    Originally Posted by AppleComputer View Post


    Marvin, what you are saying is, that if I have my encrypted images mounted and it crashes or I am forced to do a hard restart that there is a darn good chance that the read/write encrypted image will become corrupted?



    If you use sparse images, there is a greater likelihood of corruption.



    http://macosx.com/forums/mac-os-x-sy...r-failure.html



    All the time you hear of disk image corruption it's sparse images. It's possible that a fixed size one can be corrupted by a bad hard drive sector but I've never seen fixed image corruption myself. Under controlled tests, it's possible to corrupt sparse images. Like in the example above, create a sparse image, start copying and then power down. It doesn't always happen and they've probably improved them given that FileVault relies on them but I personally don't trust them.



    There are even solutions to convert FileVault to fixed size images:



    http://www.macosxhints.com/article.p...31104223355900



    But I would stick with the manual ones to control what goes on it.



    Quote:
    Originally Posted by AppleComputer View Post


    Or, are you saying that there is only really a chance of corruption if I am actively making transfers/changes to the mounted image at the time of a crash?



    It doesn't even have to be a crash but a file transfer interruption - again not always though, you can force unmount the image while it's copying or quite the Finder and it can hold up ok. But yes, it seems a power down is when sparse images are most likely to become corrupted.



    Quote:
    Originally Posted by AppleComputer View Post


    This is the kind of stuff I am most curious/concerned about. I pretty much plan on always having these encrypted images mounted. Also, did I mention that I plan on having the encrypted images on my secondary, internal hard drive? Does that make any kind of difference--mounting images ONTO the desktop FROM a secondary hard drive, and always accessing the data that way?



    Nope, accessing from an external is fine.



    Quote:
    Originally Posted by AppleComputer View Post


    Also, as I mentioned earlier, I am still using Tiger on a PPC. Will my Disk Utility-encrypted images make the transfer seamlessly when I make the jump to a new Mac down the line? From PPC to Intel, etc?



    Yes they work fine from PPC to Intel. The very early versions in 10.1/10.2 were slightly different and must have had a security exploit because if you mount them, it asks if you are sure you want to mount it but 10.4 is fine ad they are all still compatible. Apple pretty much have no choice but to make the images compatible beyond system upgrades.



    Quote:
    Originally Posted by AppleComputer View Post


    The likely hood my computer being stolen from my home, or my unencrypted backups falling into the wrong hands, is not great. Would I be at more of a data-loss risk with my proposed storage/encryption method of mostly always having these images mounted?



    No, it doesn't matter how often or long you have the images mounted, as soon as you power down, the images are unmounted and only accessible via a password. One thing to be careful of is do not save your password in Keychain when it asks during disk image creation - uncheck the box. If you save it in Keychain, the image will auto-mount without asking for your password, which means that someone stealing your machine can boot it up and do the same. Pick a password you won't forget though.
Sign In or Register to comment.